1. Field of the Invention
The present invention relates generally to gerotor hydraulic devices that can be used as pumps or motors and, more particularly, to such devices having an orbiting outer gear disposed within a cover connected to the gear machine body.
2. Description of the Prior Art
Many types of prior art hydraulic and pneumatic devices have utilized internal gear sets which are often called gerotors or rotors. Such devices can be used as pumps where shaft work is converted to hydraulic work and as motors where hydraulic work is converted to shaft work. Examples of gerotor pumps and motors are shown in U.S. Pat. Nos. 3,572,983; 4,411,607; 4,545,748; and 4,586,885. In an internal gear pump or motor, an inner gear or rotor having outwardly directed teeth cooperates with an external gear or rotor having inwardly directed teeth so that fluid chambers therebetween increase and decrease in volume as the inner and outer gears rotate in a housing. In one particular type of gerotor pump or motor, the inner gear rotates while the outer gear orbits in a cavity defined by a locating ring (a ring which locates the rotor set between the body parts) disposed radially outside of the outer gear. Extending radially along the inside of the locating ring are a plurality of cylindrical roller dowells which serve as guides to retain the outer gear in its orbital motion. These roller dowells are received in arcuate recesses on the radial outside of the outer gear. As the inner gear rotates, the corresponding motion of the outer gear is an orbiting motion because of the roller dowells being received in the arcuate recesses of the outer gear. The variable displacement chambers formed between the inner and outer gear as the outer gear orbits and the inner gear rotates function to transfer work between the fluid in the chambers and the rotating shaft connected to the inner gear.
A significant problem with the prior art arises because the locating ring is connected to the pump or motor by a plurality of bolts which receive a very significant stress as the shaft starts and stops. For example, if the shaft is connected to a wheel driven by the hydraulic power of the motor, the wheel can be subjected to significant torsional stresses, all of which are received by the bolts which hold the locating ring in the motor. Generally, the point of failure of the motor is at the bolts so that the bolts are sheared off and the motor is broken between the locating ring and the motor body. Although it is possible to make the bolts larger and the locating ring thicker, there are also often size requirements with respect to the motor which make this difficult to accomplish. Therefore, it would be desirable to strengthen the connection between the locating ring and body without increasing the size of the locating ring and bolts.
It is accordingly an object of the present invention to provide an improved internal gear motor or pump of the type having an orbiting outer gear. More specifically, it is an object to provide such an internal gear device with a reinforced connection between the locating ring and body without the necessity of increasing the size of the device or the size of the bolts. Still further, it is an object of the present invention to provide such an improvement without significant additional construction costs and having a relatively simple design.